Im putting a blower on my Single Engine Sonic 31ss with 540cu.in. do I have to change the bottom pulley becuase its huge got 4 vee's on it and a deep cup and if I mount the drive[blower] pully on it I would need 8" long bolts and noway to center it.

I just went throught the same thing.... I could not get mine to center by eyeballin it so I tightened it snug, to where you could move it with light tapping, put a dial indicater on it and turned the engine and adjust, turn the engine and adjust, until you get it right. There may be another pulley you can buy, but this works just fine for me

What are the 4? "V" belts for? Single engine boat. Alt, Power steering, raw water pump. 3 belts. You could get that down to 2 belts by running the PS and alt off of a longer belt space out the PS pump. I have a new 3 belt B&M pulley available but also there should have been a spacer that will center the ribbed pulley for you. I was blowing belts off constantly until I got the right ones from B&M.

first you need to set the blower on and see where the lower pulley needs to be, on my weiand set up, the blower pulley goes on first and you have to have a 3 groove pulley that fits inside that. Rob